For the present application, a composite element comprises fibers embedded in a resin matrix. The resin may be:                a thermoplastic resin that softens repeatedly when it is heated above a predetermined temperature and which becomes hard again below the predetermined temperature,        a thermosetting resin which becomes solid irreversibly during a polymerization step.        
According to one method of operation, the process for manufacturing an acoustic panel made of thermosetting composite comprises two polymerization steps.
During a first polymerization step, the acoustically resistive layer is produced by optionally incorporating corner pieces in order to form edges of the acoustic panel. During a second polymerization step, the cellular structure reinforced by the reflective layer is incorporated on the acoustically resistive layer.
Carrying out two successive polymerizations may prove difficult to implement, in particular in order to obtain a satisfactory attachment at the interface between the cellular structure and the acoustically resistive layer.
According to another issue, the acoustic panel made of thermosetting composite may be hard to reinforce by affixing to the reflective wall at least one layer made of high-performance thermoplastic composite since the consolidation of the layer requires a temperature rise between 300° C. and 400° C. which is incompatible with the thermosetting composites, and also with the composites that form the cellular structure.
The present disclosure aims to resolve the drawbacks of the prior art.